Our Skin Cells Can 'See' UV Rays

Below:

Next story in Science

How the skin knows to start tanning after the sun's rays hit is
somewhat of a mystery. Now researchers have found our skin may be
able to "see" the sun's ultraviolet rays using a light-sensing
pigment also found in our eyes.

"As soon as you step out into the sun, your skin knows that it is
exposed to ultraviolet radiation," said senior researcher Elena
Oancea, assistant professor of biology at Brown University. "This
is a very fast process, faster than anything that was known
before."

Ultraviolet radiation at the Earth's surface comes in two
flavors: UVA and UVB. UVB rays have shorter wavelengths, and make
up only a small portion of ultraviolet radiation from the sun.
Such rays lead to darkening of the skin days after exposure. UVB
rays are typically linked with DNA damage that can cause skin
cancer, although research has also linked UVA to cancer. UVA
rays, by contrast, have longer wavelengths and are less intense,
but account for the majority of ultraviolet radiation and lead to
skin darkening much more quickly. [ Why Skin
Cancer Is on the Rise ]

This study's findings focus on how UVA rays lead to darkening.

Oancea and her team studied the skin cells, called melanocytes,
that produce
the protective pigment melanin, and found that the cells also
contained rhodopsin, a pigment previously found only in the
retina of the eye where it detects light. They then examined how
rhodopsin in the melanin-producing cells sends out a signal when
exposed to UVA radiation. The signal instigates the production of
melanin, they found.

The team found that after an hour, measurable amounts of melanin
had begun accumulating, which would result in tanning.

The study is detailed in the most recent issue of the journal
Current Biology.